Problem: $ { \left[\begin{array}{rrr}{1} & {-2} & {1} \\ {2} & {0} & {-1}\end{array}\right]-\left[\begin{array}{rrr}{2} & {1} & {-2} \\ {2} & {4} & {3}\end{array}\right] = {?} } $
Solution: To find the difference of two matrices, subtract the corresponding items between each matrix. ${\left[\begin{array}{rrr}{1}-{2} & {-2}-{1} & {1}-{-2} \\ {2}-{2} & {0}-{4} & {-1}-{3}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{-1} & {-3} & {3} \\ {0} & {-4} & {-4}\end{array}\right]}$